After disc conversion pedal is soft when engine is running

[coffeeguy]

I did an aftermarket no-name disc conversion for a friend.  A new disc drum master was installed but the original distribution block was retained. Pedal is hard and  "normal" if the engine is off but when running is soft with a lot of travel. Have I missed something?

[myk]

I don't think this is an issue but isn't the distribution block different for this set up?

[coffeeguy]

I seem to find some say they are the same and others say no. Are the brake residuals in the old drum/drum distributor blocks?

[Mopar Nut]

Was the power booster changed?

[coffeeguy]

No . Just master.

[Back N Black]

Sounds like air in  the system.

[Dino]

Ignoring correct components at this time ie disc master and combo valve, does the car stop as it should?  Is this just a pedal feel issue or are the brakes not working properly either?

[John_Kunkel]

If the new MC is smaller in diameter than the original you'll have more pedal travel and if your front discs are single piston the pedal will be a little softer....assuming the MC was properly bench bled and there is no air in the system.

[coffeeguy]

Brakes work ok. It is the single piston caliper. The master was  properly bench bleed.  Just feel weird. and the pedal goes a little low.

[A383Wing]

you don't have the calipers on the wrong side, do ya?

bleeder screw must be at highest point....don't laugh.....I know lots of people who mixed up calipers from side to side

[myk]

I would've thought that the bleeder screws would be on the bottom...

[fy469rtse]

Nah Myk , bleeders have to be at the top , where the air in system will go , end of the line
Don't worry we have all done this , part of learning

[coffeeguy]

The bleeders are at the highest point. I am thinking maybe to small a master. It was a carquest replacement and I wouldn't know the right one from the wrong one. What diameter should the piston be for optimum  braking?

[John_Kunkel]

After my very first drum-to-disc conversion using all factory parts (singled piston calipers) I was worried about the soft pedal when the engine was running and was convinced there was air in the system. After bleeding a couple of quarts of fluid through the system I took the car to a brake shop and they felt the pedal and declared it "normal for floating calipers".

To this day I can tell a car/truck with power floating calipers, the pedal is never as firm as with drum brakes.

[coffeeguy]

Thanks John

[coffeeguy]

I am in the process of moving the distribution block(header wants to sit to close) iI notice it  has only 3/16 lines to front brakes but could take 1/4 as it has "oversize fittings to connect 3/16 to block line from master to block for fronts was 1/4. Would the larger 1/4 line  to eack wheel help?